Condensed Consolidating Financial Statements (Details 2) (USD $) In Millions	Aug. 31, 2011	May 31, 2011	Aug. 31, 2010	May 31, 2010
CURRENT ASSETS
Cash and cash equivalents	$ 1,959	$ 2,328	$ 1,709	$ 1,952
Receivables, less allowances	4,624	4,581
Spare parts, supplies, fuel, prepaid expenses and other, less allowances	770	766
Deferred income taxes	610	610
Total current assets	7,963	8,285
PROPERTY AND EQUIPMENT, AT COST	34,224	33,686
Less accumulated depreciation and amortization	18,404	18,143
Net property and equipment	15,820	15,543
GOODWILL	2,435	2,326
Other assets	1,620	1,231
ASSETS	27,838	27,385
CURRENT LIABILITIES
Current portion of long-term debt	301	18
Accrued salaries and employee benefits	1,245	1,268
Accounts payable	1,563	1,702
Accrued expenses	1,872	1,894
Total current liabilities	4,981	4,882
LONG-TERM DEBT, LESS CURRENT PORTION	1,367	1,667
OTHER LONG-TERM LIABILITIES
Deferred income taxes	1,441	1,336
Other liabilities	4,335	4,280
Total other long-term liabilities	5,776	5,616
STOCKHOLDERS' INVESTMENT	15,714	15,220
LIABILITIES AND STOCKHOLDERS' INVESTMENT	27,838	27,385
Parent Company Member
CURRENT ASSETS
Cash and cash equivalents	1,314	1,589	1,107	1,310
Spare parts, supplies, fuel, prepaid expenses and other, less allowances	38	77
Total current assets	1,352	1,666
PROPERTY AND EQUIPMENT, AT COST	25	24
Less accumulated depreciation and amortization	19	18
Net property and equipment	6	6
INVESTMENT IN SUBSIDIARIES	15,878	15,404
Other assets	1,638	1,652
ASSETS	18,874	18,728
CURRENT LIABILITIES
Accrued salaries and employee benefits	54	50
Accounts payable	42
Accrued expenses	246	198
Total current liabilities	342	248
LONG-TERM DEBT, LESS CURRENT PORTION	1,000	1,000
INTERCOMPANY PAYABLE	682	1,095
OTHER LONG-TERM LIABILITIES
Other liabilities	1,136	1,165
Total other long-term liabilities	1,136	1,165
STOCKHOLDERS' INVESTMENT	15,714	15,220
LIABILITIES AND STOCKHOLDERS' INVESTMENT	18,874	18,728
Guarantor Subsidiaries Member
CURRENT ASSETS
Cash and cash equivalents	261	279	234	258
Receivables, less allowances	3,662	3,696
Spare parts, supplies, fuel, prepaid expenses and other, less allowances	684	645
Deferred income taxes	591	598
Total current assets	5,198	5,218
PROPERTY AND EQUIPMENT, AT COST	32,422	31,916
Less accumulated depreciation and amortization	17,293	17,071
Net property and equipment	15,129	14,845
GOODWILL	1,565	1,564
INVESTMENT IN SUBSIDIARIES	2,784	2,705
Other assets	1,381	1,039
ASSETS	26,057	25,371
CURRENT LIABILITIES
Current portion of long-term debt	301	18
Accrued salaries and employee benefits	1,046	1,071
Accounts payable	1,285	1,385
Accrued expenses	1,480	1,563
Total current liabilities	4,112	4,037
LONG-TERM DEBT, LESS CURRENT PORTION	367	667
INTERCOMPANY PAYABLE	578	222
OTHER LONG-TERM LIABILITIES
Deferred income taxes	2,938	2,842
Other liabilities	3,042	3,001
Total other long-term liabilities	5,980	5,843
STOCKHOLDERS' INVESTMENT	15,020	14,602
LIABILITIES AND STOCKHOLDERS' INVESTMENT	26,057	25,371
Non Guarantor Subsidiaries Member
CURRENT ASSETS
Cash and cash equivalents	553	546	429	443
Receivables, less allowances	985	912
Spare parts, supplies, fuel, prepaid expenses and other, less allowances	48	44
Deferred income taxes	19	12
Total current assets	1,605	1,514
PROPERTY AND EQUIPMENT, AT COST	1,777	1,746
Less accumulated depreciation and amortization	1,092	1,054
Net property and equipment	685	692
INTERCOMPANY RECEIVABLE	1,260	1,317
GOODWILL	870	762
Other assets	106	63
ASSETS	4,526	4,348
CURRENT LIABILITIES
Accrued salaries and employee benefits	145	147
Accounts payable	428	430
Accrued expenses	146	133
Total current liabilities	719	710
OTHER LONG-TERM LIABILITIES
Deferred income taxes	8	17
Other liabilities	157	114
Total other long-term liabilities	165	131
STOCKHOLDERS' INVESTMENT	3,642	3,507
LIABILITIES AND STOCKHOLDERS' INVESTMENT	4,526	4,348
Consolidation Eliminations Member
CURRENT ASSETS
Cash and cash equivalents	(169)	(86)	(61)	(59)
Receivables, less allowances	(23)	(27)
Total current assets	(192)	(113)
INTERCOMPANY RECEIVABLE	(1,260)	(1,317)
INVESTMENT IN SUBSIDIARIES	(18,662)	(18,109)
Other assets	(1,505)	(1,523)
ASSETS	(21,619)	(21,062)
CURRENT LIABILITIES
Accounts payable	(192)	(113)
Total current liabilities	(192)	(113)
INTERCOMPANY PAYABLE	(1,260)	(1,317)
OTHER LONG-TERM LIABILITIES
Deferred income taxes	(1,505)	(1,523)
Total other long-term liabilities	(1,505)	(1,523)
STOCKHOLDERS' INVESTMENT	(18,662)	(18,109)
LIABILITIES AND STOCKHOLDERS' INVESTMENT	$ (21,619)	$ (21,062)